Make a note of what forum you're posting your question in and what the title of your post is. Then just browser for it starting at the forum page (linked to at the top of the page between "home" and "control panel").
Alternatively, after you post, you are taken to a page showing your question as it appears in the open thread. You can bookmark that page and just come back to it as you need to.
(Of course, my answer here assumes you'll find
this thread after having posted your question.)